3.2 chromosomes Flashcards
how is the genetic material in prokaryotes stored
- free in NUCLEOID (no nucleus)
- prokaryote DNA (‘naked dna’)
- single chromosome, circular DNA (not associated w proteins for additional packaging)
what cells have plasmids?
some prokaryotic cells
(Plasmids are additional circular DNA molecules)
what are plasmids?
small, circular DNA
- may contain one or several genes
- bacteria can easily exchange plasmids
- can self-replicate
steps to become eukaryote chromosomes 5
- dna coiled around 8 histone proteins – nucleosome
- nucleosomes linked by additional histone protein – string of chromatosomes
- coil to form solenoid structure – condensed to form 30 nm fibre
- fibres form loops, compressed and folded around proteins to form chromatin
- chromatin supercoil during cell div into chromosomes
what is the constriction point??? of a chromosome. and what are the shorter and longer sections called
centromere
shorter section – p arm
longer section – q arm
how can the unique banding patterns on chromosomes be generated
staining
what is a locus
a position of a particular gene on a chromosome
three points of reference for the region of a locus
- number/letter that denotes WHICH CHROMOSOME
- which ARM the locus is on (q or p)
- number corresponding to the G BAND location
what are organismms wtih TWO sets of chromosomes called
diploid
diploid divided by 2 =
haploid (sex cells/gametes)
what is a zygote
a diploid cell resultant from the fusion of 2 gametes
characteristics of a diploid nuclei
- nuclei possessing PAIRS of HOMOLOGOUS chromosomes (2n)
- two alleles for each trait
- all body/somatic cells are diploid
characteristics of haploid nuclei
- only 1 set of chromosomes (n)
- possess a SINGLE allele for each trait
- all gametes are haploid (from diploid cells via meiosis)
characteristics of homologous chromosomes
- carry same set of genes in diff locations
- each allele (diff versions of the same gene) comes from each parent
what are alleles
diff versions of the same gene
what are the common stuff between homologous chromosomes
- same structural features
- same genes at the same loci (may have diff allele
what is a karyotype
the number and types of chromosomes
in a eukaryotic cell
method karyotypes are determined
- harvesting cells from foetus or WBC
- chemically inducing cell division, arresting mitosis while chromosomes are condensed
(stage halted will determine if the chromosomes appear w sister chromatids)
how does a karyogram work
(it looks like all the homogolous chromosomes but 1-22 + x and y)
- chromosomes stained and photographed
- chromosomes arranged into homologous pairs according to size
why cant species interbreed
- diff diploid numbers – cannot form homologous pairs in zygotes
- offspring are infertile, cannot form functional gametes
heterosomes vs autosomes
heterosomes: determines sex
autosomes: does not
why karyotype an unborn child
- determine gender
- test for chromosomal abnormalities
down sydrome
- 3 pairs of chromosome 21
- caused by non-disjunction event
- mental and physical delays in development
what is a non-disjunction event?
seperation fails – both sister chromatids/homologous chromosomes are pulled to same pole
